diff --git a/src/script/sign.h b/src/script/sign.h
--- a/src/script/sign.h
+++ b/src/script/sign.h
@@ -210,8 +210,10 @@
 
     template <typename Stream> inline void Serialize(Stream &s) const {
         // Write the utxo
-        SerializeToVector(s, PSBT_IN_UTXO);
-        SerializeToVector(s, utxo);
+        if (!utxo.IsNull()) {
+            SerializeToVector(s, PSBT_IN_UTXO);
+            SerializeToVector(s, utxo);
+        }
 
         if (final_script_sig.empty()) {
             // Write any partial signatures
@@ -493,6 +495,7 @@
         for (const PSBTInput &input : inputs) {
             s << input;
         }
+
         // Write outputs
         for (const PSBTOutput &output : outputs) {
             s << output;
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -220,7 +220,7 @@
 bool SignPSBTInput(const SigningProvider &provider,
                    const CMutableTransaction &tx, PSBTInput &input,
                    SignatureData &sigdata, int index, SigHashType sighash) {
-    // if this input has a final scriptsig, don't do anything with it
+    // If this input has a final scriptsig, don't do anything with it.
     if (!input.final_script_sig.empty()) {
         return true;
     }